The Insurance Institute for Business & Home Safety (IBHS)has conducted a full-scale research test program of how wind-drivenwater, such as that occurring during hurricanes, penetrates openings in residential roofsystems.

“Wind-driven rain that gets into a house through openings in theroof can collapse ceilings and cause extensive damage to interiorfinishes, furnishings, and other family possessions,” said JulieRochman, president & CEO at IBHS. “The testing conducted by ourengineers clearly demonstrated that water penetration duringhurricanes could be substantially reduced by sealing the roof deckseams.”

For new construction or re-roofing, roof deck seams can besealed from the exterior using a modified bitumen tape. Forretrofitting when the roof cover is not replaced, homeowners canseal the roof deck seams from the inside with a closed-cell foamspray adhesive.

IBHS researchers built a 1,300-square foot, single-story duplextest building with construction features common in many coastal andinland areas of the Atlantic and Gulf Coast states with hurricaneexposure. The interior of the duplex was furnished. Both sides ofthe duplex roof were identical, with the critical exception ofusing modified bitumen tape to seal the between-sheathing jointsand gaps on one side of the roof.

The building was placed inside a 21,000-square foot testchamber and subjected to several individual test sequencesinvolving high-speed, multi-directional, gusty winds and prolongedexposure to the typical amount of rain during a hurricane,delivered at a rate of up to eight inches per hour. Video footageof the interior of both sides of the building filmed during thetest showed water entering the side with the unsealed roof deck,streaming off of light fixtures and ceiling fans. Approximately 30minutes after the completion of the test, portions of the ceilingon the unsealed side began to collapse.

“In the real world, a family would be uprooted from the homewithout the sealed roof deck, potentially for months while repairswere made,” said Dr. Anne Cope, IBHS research director. “However, afamily living in the home with the sealed roof deck could probablystay in the home while repairs were made, and if they did have toleave, then they would likely be able to return to the home muchsooner.”

Following the test, IBHS brought in a trained claims adjuster toestimate the amount of damage each house suffered. He assessed thedamage to the front three rooms on both sides of the duplex,including the kitchen, dining room, and family room. During ahurricane or high wind event, winds generally come from arelatively small range of directions after aroof cover has blownoff, so damaged is usually confined to one area of a house.

According to the adjuster's report, estimated damage on theunsealed side totaled nearly $17,000, while estimated damage on thesealed side totaled approximately $5,400. Of particular note isthat the furniture in the side with the unsealed roof deck had tobe replaced, while the furnishings in the side with the sealed roofdeck only had to be cleaned.

“Sealing the roof deck can significantly strengthen thiscritical part of a home and reduce the chances of a catastrophicloss due to water damage when the roof covering is compromised orblown off entirely during a high-wind event. And taping the seamson an average-sized roof costs only about $500, a great, relativelysmall investment that could pay huge dividends when a storm hits,”Cope added.